Databases are used to store data and provide structured access to that data. Databases can be small such that they are able to be contained and accessed on a single computer system. An example of this might be an individual's personal financial data. Databases also can be large and distributed over more than one location. An example of this might be an airline reservation system that contains information on every seat on every flight operated by an airline and needs to be accessed in real time from numerous locations to make, check and change reservations. In general, despite differences in size, design, access frequency and contents, databases should provide reliable access to accurate data in a timely fashion.